1. Field of the Invention
This invention relates to a tube fitting and more particularly to a tube fitting suitable for use in both pressure and vacuum applications.
2. Discussion of the Prior Art
Tube fittings of the swage variety, such as those manufactured by the Crawford Fitting Company under the tradename Swagelok and the Parker Hannifin Company under the tradename Parker CPI, have been used for many years to connect various types of tubing, including glass tubing, to other structures. These fittings are widely used in scientific and commercial applications where either high pressure or vacuum are involved. With moderate pressure applied by a nut to a ferrule carried by the tube, a reasonable leak-tight fitting between the tube and the structure can be obtained. However, the friction between the nut and the ferrule tends to rotate the ferrule as the nut is tightened, and the friction between the ferrule and the tube tends to rotate the tube as well. Under some circumstances, this does not present much of a problem, but in rigid systems, particularly fragile systems such as those composed of glass, any rotation of the tube as the nut is tightened introduces stress into the system. In extreme cases, this can cause fracture of the glass.
It has now been found that a simple modification to the nut utilized with the swage fitting will reduce the possibility of such fracture by immobilizing the ferrule as the nut is turned.